The Wideband Code Division Multiple Access (WCDMA) is a technique used in the third generation (3G) wireless communication system based on and developed from Code Division Multiple Access (CDMA). WCDMA has evolved continuously towards higher data rates and towards packet-switched IP-based services. The High-speed Downlink Packet Access (HSDPA) technology has been designed to enhance WCDMA by increasing downlink packet data throughput via fast physical layer (L1) retransmission and transmission combining, as well as fast link adaptation controlled by the Node B, otherwise known as the Base Transceiver Station (BTS).
In WCDMA, three transport channels, Dedicated Channel (DCH), Downlink-shared Channel (DSCH), and Forward Access Channel (FACH), may be used for downlink packet data. The DCH may be used for any type of service in the downlink direction. The DSCH operated together with a DCH to define channel properties best suited for packet data needs while leaving the data with a tight delay budget, such as speech or video, to be carried by the DCH. The FACH can be used for downlink packet data as well. The FACH is operated normally on its own and sent typically at rather high power level to reach all users in the cell, owing to the lack of physical layer feedback in the uplink.
To implement the HSDPA feature, three new transport channels, High Speed Downlink-Shared Channel (HS-DSCH), High-speed Shared Control Channel (HS-SCCH), and Uplink High-Speed Dedicated Physical Control Channel (HS-DPCCH), are introduced in the physical layer specifications. The HS-DSCH carries the user data in the downlink direction, with the peak rate reaching up to, for example, 10 Mbps with 16 QAM (quadrature amplitude modulation). The HS-SCCH carries the necessary physical layer control information to enable decoding of the data on the HS-DSCH and to perform the possible physical layer combining of the data sent on the HS-DSCH in the case of retransmission of an erroneous packet. The HS-DPCCH carries the necessary control information in the uplink, namely, downlink quality feedback information, for example.
In WCDMA/HSDPA system, transmissions from a single source are separated by various channelization codes. The channelization codes of WCDMA/HSDPA are based on the Orthogonal Variable Spreading Factor (OVSF) technique. The use of OVSF codes allows the channelization codes to be changed and orthogonality between different channelization codes of different lengths to be maintained.
Various signaling information is communicated between the network and the terminals. The common pilot channel (CPICH) is an un-modulated code channel, which is scrambled with the cell-specific primary scrambling code, in order to provide channel estimation at a terminal or user equipment (UE). The CPICH is measured at the terminal to enable features such as handover and cell selection and/or reselection. The quantities defined that can be measured by the terminal from the CPICH are Received Signal Code Power (RSCP), Received energy per chip in the band (Ec/N0).
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.